In many cases, slab coverings are laid using what is called a thin-bed method, with an appropriate contact adhesive being utilised in order to affix the slab coverings to the ground. Owing to varying degrees of thermal expansion between the surface lining and the ground and to the tensions associated with this, cracks may occur in the surface lining, which may ultimately lead to a detaching of parts of the surface lining.
In order to reduce such tension differences, DE 37 0441 4 A1 proposes a support plate made of a foil-like plastic material and comprising dovetailed grooves that are alternately open towards both sides, such that under conditions of compressive stress and tensile load said plate is movable in a cross-direction with respect to the extension of the grooves. On one side of the support plate, a net-like, non-woven fabric is provided in order to connect the support plate with the ground, for example a screed, and to achieve an enhanced bonding effect with an adhesive. This support plate has the disadvantage of being limited to one direction of expansibility and/or compressibility, which is a cross-direction with respect to the longitudinal extension of the dovetailed grooves. A support plate of this type is often not capable of ensuring the necessary tension reduction.
In order to achieve said tension reduction in both directions, a support plate has been proposed, according to DE 299 24 180 U1, which comprises embossings intersecting one another on one plate side so as to form, and circumferentially delimit, closed chambers. The chambers serve the purposes of receiving an adhesive or mortar and of forming adhesive or mortar stilts, which enables the formation of a tight bond with the adhesive or mortar layer and the surface lining affixed thereto. With said intersecting embossings, a foil-like plate is proposed which may be expanded or compressed, at least to a small extent, in both directions of the plane in which it extends, so that differences in tension between the ground and the surface lining may be absorbed by the support plate. In addition, the chambers have undercuts so that the adhesive or mortar stilts introduced into the chambers become caught in the undercuts of the chambers.
This configuration has the disadvantage that in the region of the undercut, the mortar stilts have a narrowing as compared to their post surface within the bottom of the chamber and that in the region of the narrowing, crack formation is an issue and the upstanding post members inserted into the chambers may become detached from the mortar layer resting on top of them. The positive interlocking initially provided by the undercut is severed by the formation of cracks occurring on the level of the narrowing. The tight bond no longer exists and the tension reduction between the ground and the surface lining is no longer possible.
DE 20 2005 004 127 U1 discloses a support plate made of a foil-like plastic material to be used in slob-faced floor, wall, or ceiling constructions which comprises a support plate consisting of a foil-like plate having recesses without undercuts. These recesses either have wall portions extending vertically between the one plate side and the outer end faces or have conically tapered wall portions. On the plate side from where the recesses extend, a net-like, woven or non-woven fabric covering or overlapping said recesses is provided, which is to say that the woven or non-woven fabric is realised in the form of a layer extending in a plane and spanning said recess. Owing to said net-like nature of the fabric, this configuration makes it possible for the adhesive or mortar layer that is to be applied thereto to permeate through the non-woven fabric overlapping the recesses and pass into said recesses and become bonded. Introducing the adhesive or mortar layer into the recesses will thus lead to the formation of adhesive or mortar stilts which become bonded with the woven or non-woven fabric, said non-woven fabric fully traversing the mortar stilt. This support plate makes it possible to satisfactorily reduce tensions occurring between the ground and the surface lining and to ensure a continuous decoupling as well as a secure fixation of the surface lining. However, the requirements that have to be met by such support plates are ever increasing.